1. Field of the Invention
This invention relates to a spontaneous light-emission-type plasma display panel (PDP) using a gas discharge.
2. Description of the Related Art
Recently, it has been anticipated to put into practical use a plasma display panel of surface-discharge-type alternating-current driving system as a large-sized, thin color display unit.
FIG. 4 shows an example of the structure of a plasma display panel of alternating-current driving system, which will now be described with reference to the drawing.
As shown in FIG. 4, a plurality of pairs of line electrodes X and Y disposed in parallel to each other are formed on a glass substrate 1 on a display surface side, the line electrodes including transparent conductive films as transparent electrodes, and metal electrodes in the form of metal films stacked up in end portions opposite to the discharge gaps of the respective transparent conductive films and used for supplementing the conductivity of the transparent electrodes. Further, a dielectric layer 2 is formed so as to cover the line electrodes X and Y, and a protective layer (not shown) of MgO is also formed on the dielectric layer 2.
On the inner surface of a back-side glass substrate 3 lie a plurality of column electrodes 4 disposed with a predetermined space held therebetween in such a way as to cross the pairs of line electrodes X and Y at right angles, and an electrode protective layer 5 for covering the column electrodes 4. Further, a belt-like rib (partition wall) 6 having a predetermined height is provided between the column electrodes 4 of the back-side glass substrate 3, whereby a discharge space 7 is formed in each unit luminous area in the direction of a display line to define the gap dimension of the discharge space 7. Moreover, fluorescent material layers of three colors R, G and B are provided above the surfaces of the column electrodes 4 of the back-side glass substrate 3, and the sides of the ribs 6, respectively.
A process of making the plasma display panel comprises the steps of placing the aforementioned component elements on the respective glass substrates, applying frit paste containing low-melting glass powder as the main ingredient so that a display area is surrounded with the paste in one outer peripheral non-display area of the glass substrate, and temporarily calcining the paste in order to form a sealing layer 10 first.
In such a state that both the glass substrates have been combined together and temporarily fixed, the combination is then subjected to heat treatment at about 400xc2x0 C. so as to fusion-bond the two sheets of glass substrates 1 and 3 using the sealing layer 10. Subsequently, the interior space is evacuated and also a rare gas is encapsulated therein.
Since the frit paste containing the low-melting glass powder as the main ingredient is employed for the sealing layer 10 used to seal the peripheries of the two sheets of glass substrates 1 and 3 in the conventional plasma display panel, the generation of thermal decomposition gas tends to become greater when the peripheries thereof are sealed through the heat treatment. Consequently, the residual moisture and impure gases such as carbon dioxide and the like left or adsorbed by the sealing layer 10 are exhausted through the heat treatment at a predetermined temperature during the step of evacuation. However, the problem is that the impure gases diffused in the discharge spaces may contaminate the protective film used to cover the dielectric layer 2 and this results in making discharge characteristics unstable.
The present invention has been made to solve the above problem with the prior art, and therefore an object of the present invention is to provide a plasma display panel with improved reliability.
To achieve the above object, according to the present invention, there is provided a plasma display panel wherein a sealing layer is used for sealing the peripheral edge portions of a pair of glass substrates and wherein first partition walls for respectively providing discharge spaces in a display area between the glass substrates, is characterized by providing a second partition wall which is so disposed as to surround the display area inside the sealing layer and is brought into intimate contact with the pair of glass substrates.
In the plasma display panel, the first and second partition walls are formed by simultaneously patterning low-melting glass layers formed on the respective glass substrates according to the respective patterns.
The plasma display panel is arranged so that the first partition walls for partitioning the display area into discharge spaces in between the glass substrates, and the second partition wall kept in close contact with the pair of glass substrates is provided in such a way as to surround the display area, so that the display area remains unaffected by the formation of the sealing layer in the peripheral edge portion of the glass substrate.
Since the first and second partition walls are formed by simultaneously patterning the low-melting glass layers formed on the respective glass substrates according to the respective patterns, moreover, the steps of forming these partition walls can be carried out efficiently and simplified at the same time.